| Humidity is used to indicate the quantity of steam in the air, it is a basic parameter of meteorological observation. Humidity measurement has been the most difficult parameter of the meteorological observations. Macromolecule capacitance type humidity sensor (humicap) has already become the most widely used humidity sensor presently.Humidity sensitive material used as humidity sensing layer is the core for constituting the humidity sensor. Presently the hot researching macromolecule humidity sensitive materials mainly include polyimide, polyphenyl acetylene, polysulfone, Plasma Polymerization polytene, linear Cross bonding plasma polymerzation polymetharrylic acid methyimethacrylate, etc., the humidity materials have wide resources, and are easy to produce, machine, and can acquire different physical and chemistry quality by altering the molecule structure.Polyimide ("PI" for short) is a sort of polymer regarding imide-substance as the character, this sort of polymer has a series of advanced performance which other material can/not match, these virtues include distinct hardness, abrasive resistance, excellent mechanics/optical performance, and chemistry stability, thus the material is widely used in high tech areas including aerospace, aviation, atomic energy, film separation technique, precision and important mechanical and electrical products, LCD display, etc. Meanwhile, as polyimide has distinct heat resistance, dielectrical property and good radio resistance, it has an increasing application as functioning material in the area of micro electronic industry and large/super large integrated circuits. In recent years, polyimide as a sort of good humidity sensing material has gotten increasing research and attention. By using polyimide as the humidity sensing film and placing it between parallel plate condenser as medium to make the capacitance type humidity sensor, the sensor will has virtues including fast response, high sensitivity, wide output scope, small dampness hysteresis error, good temperature performance and long term stability, etc., thus the material is highly noticed in the area of humidity sensor, it is a new and promising humidity sensor sensing material.The task is mainly divided into the following five parts:(1) Synthesis and characteratization of polyimide monomer containing sulfonyl,(2) Preparation and property studies of the films of polyimide containing sulfonyl;(3) Preparation and property studies of the films of biphenyl type polyimide;(4)The aging performance studies of biphenyl type polyimide films;(5)Manufacture and property studies of the polyimide humicaps.Firstly, using4,4’-o-Hydroxydiphenyl Standard (BPS) and parachloronitrobenzene(4CNB) as the material, let them react in the component solvent of toluene and N,N-dimethylformamide (DMF), and to synthesize the nitro compound4,4’-double (4-nitrophenoxy) diphenyl sulfone (BNDPS) by nucleophilic substitution reaction, then aquire the diamino substance4.4’-double (4-amidophenoxy) diphenyl sulfone (BADPS) by reduction reaction with activated carbon, hydrazine hydrate, ferric chloride. And use FT-IR、DSC to give illustration for the monomer melting point and character absorption peak.Secondly, use diamine monomer BADPS and other types of diamine monomer3,3’,4,4’-diphenyl ether tetracarboxylic dianhydride (DADPE), and4,4’-diamido-3,3’-dichlone Diphenyl methane (MOCA) to react with a kind of dianhydride monomer3,3’,4,4’-pyromellitic dianhydride (BPDA), and acquire a series of solvent of polyimide containing sulfonyl, by filming, imidization, the according polyimide film will be acquired, and then carry performance research and analyzing. The results show that the polyimide films containing sulfonyl have excellent performances.Later, put BPDA monomer、DADPE monomer、DADM monomer into certain sum of strong polarity aprotic solvent to stir to make them have thorough reaction. thus acquire series of biphenyl type polyamic acid (PAA) solvent. By filming, imidization. cooling to the room temperature, demoulding, baking, and the according biphenyl type polyimide films will be aquired. Meanwhile, test and measure a series of performance data, including comparing the various performance results like non-aging, aging100h, aging300h, to study the aging resistant performance. The results show that, biphenyl type polyimide films have excellent overall performances. The dielectric constant of the films are between3.0-3.5, the maximum tensile strength is124.4MPa, the maximum transmittance of the films is more than90%, the surface energy is between45-55mJ/m2, the water absorption is less than2%. The series films of aging in a high temperature environment, the performance change is small, which indicates the films have a long term usage under high temperature.Through the above comparing study of self-made series polyimides by molecule structure design in lab, choose the biphenyl type polyamic acid containing sulfonyl with excellent general performance as the material of humicap. and give research and discussing for the humicap’s dampness hysteresis, sensitivity, response time, degree of linearity, etc. The comprehensive performance polyimide humidity capacitance was made, and has been stereotypes mass produced by Meteorological Science and Technology Co., Ltd. in Shanghai. |
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